BUCKLING OF THICK ORTHOTROPIC CYLINDRICAL-SHELLS UNDER COMBINED EXTERNAL-PRESSURE AND AXIAL-COMPRESSION

A formulation based on the three dimensional theory of elasticity is e mployed to study the buckling of an orthotropic cylindrical shell unde r combined external pressure and axial compression, A properly defined load interaction parameter expresses the ratio of axial compression a nd external pressure loading, and critical loads are thus derived for a given load interaction, The results from this elasticity solution ar e compared with the critical Loads predicted by the orthotropic Donnel l and Timoshenko nonshallow classical shell formulations. Two cases of orthotropic material are considered with stiffness constants typical of glass/epoxy and graphite/epoxy, Furthermore, two eases of load inte raction are considered, representing a relatively high and a relativel y low axial load. For both load interaction cases considered and for b oth materials, the Donnell and the Timoshenko bifurcation points are h igher than the elasticity solution, which means that both shell theori es are nonconservative, However, the bifurcation points from the Timos henko formulation are always found to be closer to the elasticity pred ictions than the ones from the Donnell formulation. An additional comm on observation is that, for a high value of the load interaction param eter (relatively high axial Load), the Timoshenko shell theory is perf orming remarkably well, approaching closely the elasticity solution, e specially for thick construction, Finally, a comparison with some avai lable results from higher order shell theories for pure external press ure indicates that these improved shell theories seem to be adequate f or the example cases that were studied.